查看更多>>摘要：? 2022 Elsevier B.V.The doping of Hf0.5Zr0.5O2 has attracted increasing attention because of the further regulation of structure and ferroelectric properties. Here, Sr doped Hf0.5Zr0.5O2 (Sr:HZO) ferroelectric films have been prepared by chemical solution deposition on Pt/Ti/SiO2/Si substrate, and the effect of Sr doping on the structure and ferroelectric properties of Sr:HZO films was investigated. It is observed that Sr doping can further promote the formation of ferroelectric orthorhombic phase at low content (≤0.50%), inducing the enhancement of ferroelectricity. And the optimal ferroelectricity with remanent polarization of 14.63 μC/cm2 and coercive field of 1.08 MV/cm is achieved in the 0.50% Sr doped HZO film. The decrease in leakage current density with increasing Sr content is observed, which is mainly ascribed to the reduction of grain boundaries caused by the increase of grain size. Most significantly, Sr doping induces an improvement in the endurance, and a good endurance of 109 cycles without breakdown is achieved in the 0.50% Sr doped sample. These findings indicate that Sr is a potential candidate dopant for improving the structure and ferroelectric properties of HZO films.
查看更多>>摘要：? 2022 Elsevier B.V.In spite of existing experimental evidence for phase transitions of the γ′-Fe4N phase at high-pressure/high-temperature conditions, some controversy about its pressure/temperature stability range prevails in recent literature. In the present work, a thermodynamic database allowing the calculation of phase equilibria, involving the solid phases in the Fe-rich part of the Fe–N system at high-pressure conditions, is presented. For this, an existing database, which describes the atmospheric-pressure phase equilibria of Fe–N phases up to N contents of 33 at% N, has been extended by equation of state parameters describing the molar volume as a function of temperature, pressure and composition. For the pure Fe side, equation-of-state (EOS) parameters from the literature have been used. Corresponding EOS parameters for the Fe–N phases have been derived from literature data as well as own experimental data on the compression and thermal expansion behaviour and volume-composition data. On basis of the so-obtained database, phase equilibria up to a pressure of 13 GPa have been calculated. The agreement of calculated phase equilibria and own previously published experimental results is reasonable. In the presently calculated P–T projection of the univariant equilibria in the system, the phase region of the γ′ phase terminates in a quadruple point at 5.0 GPa and 713 K. This further substantiates the conclusion drawn from own previous experimental results, according to which the γ′ phase region terminates at 5.0?0.5+1.1GPa and 648?25+56K.
查看更多>>摘要：? 2022 Elsevier B.V.At present, the design of highly efficient and stable oxygen electrocatalysts for water-splitting cells in alkaline medium is predominantly limited by the sluggish kinetics for the oxygen evolution reaction (OER). This study proposes a facile and reproducible synthesis process to nurture the hierarchically porous Ni3S2 arrays on nickel foam (Ni3S2@NF) for use as a catalyst. For the hydrothermal synthesis reaction, ultrathin nanorod heazlewoodite Ni3S2 catalysts on NF is synthesized by controlling the amount of hydrazine (2 mL) and the processing time/temperatures (150 ℃ for 12 h). Due to the hierarchically porous nanorod morphologies, Ni3S2@NF under O2-saturated 1 M KOH aqueous solution shows excellent OER performance, with a low overpotential of 263 mV at a current density of 100 mA?cm?2 and a Tafel slope of 72 mV?dec?1. Further, Ni3S2@NF shows stable potential behavior at around 1.521 V under the constant current operation of 50 mA cm?2 for 50 h. Ni3S2@NF also shows negligible performance degradation during the constant current (at 50 mA cm?2 for 50 h) and voltage cycling (1.25–1.65 V for 1000 cycles) tests in a 1 M KOH solution. The excellent catalytic performance of Ni3S2@NF can be attributed to the hierarchically porous and ultrathin nanorod structures, the multi-valence-state character of Ni element, and the synergistic effect of NF, and high intrinsic catalytic active electrocatalysts for the OER.
查看更多>>摘要：? 2022 Elsevier B.V.A novel prepared ZIF-4@CuO is proposed as lithium-ion battery (LIB) anode material in this work. ZIF-4-CuCl2 is prepared by the hydrogen extraction reaction in which CuCl2 replaced the hydrogen sites on the imidazole-based N-heterocyclic carbene of ZIF-4 for under basic conditions. ZIF-4@CuO was prepared by decomposition of ZIF-4-CuCl2 precursor. The formed CuO was isolated and highly dispersed by the ZIF-4 frame. The combination of porous structure by ZIF and highly dispersed CuO nanoparticles strongly promotes the reaction kinetics of the electrode. The reversible specific capacity of ZIF-4@CuO anode material is 425 mA h g-1 at 1000 mA g-1 after 300 cycles, exhibits excellent electrochemical performance in LIBs. The preparation of highly dispersed nanoparticles explores a novel strategy for the anodes design of LIBs with superior performance.
查看更多>>摘要：? 2022 Elsevier B.V.Coarsening of the basketweave α + β microstructure in Ti-6Al-4V is a common phenomenon that occurs during thermal cycling in both additive manufacturing and cyclic heat treatment. Such a coarsening process is driven by multiple dissolution and precipitation transformations rather than by conventional Ostwald ripening. It is clear that during the first cycle, the complete dissolution of the thinnest α plates at the heating stage provides large spaces for surviving plates to regrow at the cooling stage, which results in coarsening after the first cycle. However, it is still unclear how the α plates continue to vanish and the remaining α plates sustainably coarsen in the repeated thermal cycles. In this study, cyclic heat-treatment experiments and phase-field simulations were conducted to illustrate the mechanism of sustained coarsening during thermal cycling. It was found that in addition to the complete dissolution of the thinnest α plates in the first thermal cycle, α-plate vanishing continued during repeated thermal cycling in two ways, which has not been reported before. The origin of such sustained vanishing of α plates is related to the Gibbs–Thomson effect. Moreover, the influences of cycling frequency and total duration on the transformation coarsening are detected. Both the experimental and simulation results indicate that long cycling duration results in severe coarsening, while for a given duration time, the final coarsening of the α plates is almost independent of the cycling frequency.
查看更多>>摘要：? 2022 Elsevier B.V.Coarse eutectic phases generally exist in cast alloys and have dramatic effects on mechanical properties and corrosion behaviors. Therefore, it would be convenient and feasible to modify the mechanical properties and corrosion behaviors via tuning the eutectic phases. Herein, sub-rapid solidification (SRS) is employed to modify the microstructure, especially the eutectic phase of Mg-4.5Al-1.5Sn-0.5Ca alloy. Our results reveal that SRS followed by homogenization treatment not only reduces the grain size of α-Mg matrix, but also spheroidizes and refines the large stick-like CaMgSn phase to ~1 μm. The pronounced structure modification leads to a superior strength-ductility synergy of SRS alloy, i.e., an ultimate tensile strength (UTS) of ~236 MPa and an elongation to failure (?f) of ~24%, in comparison to the alloy prepared via conventional solidification, with an UTS of ~220 MPa and an ?f of ~21%. Moreover, the homogenized SRS alloy exhibits homogeneous corrosion with increased corrosion rates of ~145 and ~2739 mm y?1 at 25 and 93 °C, respectively. It is mainly owing to the large contact area and short distance between CaMgSn and α-Mg matrix derived from the refined CaMgSn particles in SRS alloy. Our work proposes a novel degradable magnesium alloy and a processing method to prepare degradable magnesium alloy by structure modification, which is different from conventional addition of Cu, Fe, Ni elements. The novel degradable magnesium alloy shows great advantage in avoiding the residue of large amount of insoluble coarse eutectic phases, which would block the horizontal wells.
查看更多>>摘要：? 2022 Elsevier B.V.The overuse of norfloxacin (NOR) has attracted wide attention because of the persistence and bio-accumulate in ecosystems and the negative impacts on human health. To solve the environmental issue, BiOI/TiO2 p-n heterojunctions have been developed and decorated with a porous ZIF-8 to obtain novel hollow BiOI/TiO2/ZIF-8 heterojunctions, which were further characterized by XRD, SEM, HRTEM, XPS, BET, UV–vis DRS, photoluminescence, ESR, photocurrent and EIS analyses. The BiOI/TiO2/ZIF-8 heterojunctions exhibited evidently improved photocatalytic performance compared with pristine BiOI, TiO2 and BiOI/TiO2 composites under visible light irradiation. ZIF-8 plays a key role in both the enhancement of adsorption and the photocatalytic activity in NOR removal. ·O2- and ·OH radicals were the two dominating active species in the photocatalytic process according to the trapping experiments. In 2-BTZ system, large specific surface area, highly effective charge carrier migration with inhibiting recombination, more negative CB and positive VB to generate more active ·O2- and ·OH species resulted in superior photocatalytic activity. This work provides a new idea to design a kind of photocatalytic heterostructure with more active species for potential application in the field of environmental treatment.
查看更多>>摘要：? 2022 Elsevier B.V.Development of efficient and reliable transition metal-based oxygen evolution reaction (OER) catalysts has profound implications to achieve carbon-neutral economy in the future. Herein, a novel hybrid OER catalyst of heterogeneous FeNi2S4/Ni3S4 nanoparticles embedded CNT networks (FeNi2S4/Ni3S4@CNT) was prepared by a facile one-step hydrothermal reaction. The ultrafine heterogeneous nanoparticles of FeNi2S4 and Ni3S4 embedded CNT can expose abundant active sites and enhance the electrochemically active area; the electronic structure modulated by the bi-metallization of FeNi2S4 via partial substitution of Ni with Fe; the robust contact between conductive FeNi2S4 and Ni3S4 nanoparticles with abundant active sites on the surface and the CNT network with high conductivity can effectively promote the electron transfer; the 3D network with rich nanopores is beneficial to electrolyte penetration and gas release. These above merits and synergistic effects of FeNi2S4 and Ni3S4 endow the catalyst superior OER performances with an ultralow overpotential of 247 mV for the current density of 10 mA cm?2, a low Tafel slope of 53.7 mV dec?1 and remarkable durability over 20 h, surpassing those of commercial OER catalyst RuO2. This work provides a synergistic OER boosting strategy via bi-metallization, heterogeneous nanoparticle distribution and conductive skeleton to develop non-precious-based electrocatalyst by a facile one-pot synthesis method.
查看更多>>摘要：? 2022 Elsevier B.V.Cu/NiFe multilayers with different structures were fabricated by electroplating for electromagnetic wave interference shielding in the high-frequency region. The electromagnetic wave interference shielding effectiveness of the symmetric, asymmetric, and thickness-gradient multilayer films was evaluated to optimize these structures. The thickness of the NiFe layer, which acts as an interlayer between Cu layers, is an important factor. The five-layered thin film (S9), with a thickness gradient that continues to increase toward the lower layer, shows an electromagnetic interference shielding effectiveness of ? 74 dB in the wideband region, even though the total thickness of the multilayer is 1 μm. Focused ion beam, scanning electron microscopy, vector network, X-ray diffraction, four-point probe, and inductively coupled plasma–optical emission spectroscopy analyses were performed to characterize the multilayered Cu/NiFe thin films.
查看更多>>摘要：? 2022 Elsevier B.V.Metal antimony (Sb) has excellent electrical conductivity and high theoretical capacity of sodium storage based on alloy reaction mechanism and possesses great application potential in sodium ion batteries (SIBs). However, serious material fracture and volume expansion during the alloy reaction greatly hinder its commercialization process. To overcome these issues, herein a construction method combining ordered silica template, viscous sol casting and high temperature gel reduction is proposed for fabricating ordered 3D antimony/carbon inverse opal framework (3D Sb/C). With the confining effect of the templates, active antimony nanoparticles are highly dispersed. After the etching process, macroporous inverse opal framework can be constructed. The following repeated oxidation and reduction process on active antimony modifies the surrounding microscopic environment, further forming a huge number of mesopores, and finally resulting in the formation of multi-level porous structure. The acquirement of the 3D Sb/C inverse opals realizes the multiple engineering modulations for SIB application, which is conducive to the exposure of active sites, the buffer of volume expansion, and the path of rapid ion diffusion/electron transfer. Benefiting from these structure advantages, the 3D Sb/C 250 inverse opals exhibit excellent sodium storage capacity (550.4 mAh g?1 at 0.1 A g?1) and cyclic stability (257.9 mAh g?1 after 200 cycles at 1 A g?1).
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